Pioneers

1900 / 1930 ...

At the end of the nineteenth century, the invention of the internal combustion engine
made it possible for the pioneers to develop full-sized models with an adequate power source,
was in this time when the real flying control problems were found ...

1905, May 5 : Jan Bahyl ( Austro-Hungary )
On 13 August 1895, he was granted a patent numbered 3392 by emperor Franz Joseph. On the following
years he made several attempts reaching a height of 0.5 meters in 1901 , 1.5 in 1903 and on
5th May of 1905 at Pressburg he flew up using his petrol-engine helicopter to a height of 4 meters for
over 1500 meters that was also recorded by the International Airship Organisation.

Near Lisieux, Normandie in France Paul Cornu is the first to take off vertically with its pilot and make a free flight.
The machine was stabilized with sticks by men on the
ground because of its poor controllability

“Although the Cornu machine was reported by many to have made several tethered flights of a few seconds at low altitude, a very simple aerodynamic (momentum theory) analysis of the machine shows that these claims are exagerated. It is recorded in Boulet (1982) that each rotor of the Cornu machine was approximately 20~feet in diameter, and the machine had a gross weight (with pilot) of about 575~lbs. Assuming each rotor lifted half of the total weight, then the minimum possible power required at each rotor shaft would be 20.5~hp That is, with two rotors a total of at least 41~hp would be required for flight, even if the rotors were 100% efficient and there were no transmission losses (remember that only 24~hp was available from Cornu's engine).
Realistically, we could expect an efficiency of no more than 50% for the rotor(s) used by Cornu, and transmission losses (the rotors were driven by belts) of at least 10%. This means that to hover free of the ground, the installed power required would be about 90~hp. Even in ground effect, the power required to show some daylight under the wheels would have been at least 60~hp, so with only 24~hp on board it is highly improbable that Cornu 's machine ever flew free of the ground.
A similar analysis will show that the French Breguet quadrotor machine of the same year (or thereabouts) came much close to flying successfully than Cornu's machine.”
Gordon Leishman, Prof. of Aerospace Engineering, University of Maryland, USA

Military Interest in the helicopter during World War I
contributed to its advancement also. Von Karman and Petrosczy, both from Germany,
and the Hungarian Asboth intend to produced, without success, a lifting device
to replace kite balloons for observation consisted of two superimposed lifting propellers.

1912 :Ellehammer ( Denmark )
His model used a 36 hp air-cooled radial pistol-engine and
two superimposed airscrews rotating in opposite directions.
It flew, but never rose higher than 4 feets.
He made interesting technical advances but
due his solitary way of life several of them had to await reinvention by
later pioneers.

It was not until the late period of World War I that major
helicopter advances were made. The quality and quantity of production
materials increased, and great improvements were made in the field of
engine technology. With better technology and more need, the next step
in helicopter advancement would soon come.

1922 : Geogrij de Bothezat ( USSR ) Built for the US Army Air Service

co-worker James Rix photo

1924 : Louis Brennan ( Great Britain )
Had a different approach to solving the problem of torque reaction
by powering the single rotor with propellers mounted on the blades themselves.
Control was achieved by the use of servo-flaps or "ailerons" inboard of the
propellers. While Brennan's work was initially carried out with considerable
secrecy, in 1921 the machine flew successfully inside a balloon shed. Further
flights outdoors were undertaken through 1925, where the machine made
flights at low altitude. The machine crashed on its seventh flight,
and official interest in the Brennan machine quickly faded because of
increasing interest in the autogiro.

1924 : Pescara ( Argentina )
He produced several models between 1919 and 1925 in Spain and France.
He built a coaxial helo with a gross weight of 850 kg and a speed
of 13 km/h that was
the first flyable with collective and cyclic controls

The historical moment when Etienne Oehmichen is
carrying out in the presence of a French Air Ministry official.
Photo donated by the
Gunby Photo Archive

1928 : D'Ascanio ( Italy )
He constructs a helicopter with two coaxial rotors. Flap hinges and free-feathering hinges. Control by servo tabs on the blade. Held records for altitude, endurance, and distance.

Established major altitude record for an helicopter in 18 m

1928 : Hafner AR III / V ( Austria )

1920/36 : Juan de la Cierva Gyrocrafts ( Spain )

His invention of the hinged, flapping rotor blade,
made possible the development of practical helicopters.

1928 :
Juan de la Cierva made the first English Channel crossing with his C-8 Autogiro.